The present invention relates generally to intraluminal surgery, and more particularly to an improved instrument for and technique of transluminally opening any constricted regions of a passageway through a portion of a living body, and in particular, the prostatic urethra of an enlarged prostate.
As is generally well known the prostate is located at the base of the bladder, where it surrounds a portion of the urethra, the tube connecting the bladder to the outside world. The function of the . prostate is to produce a fluid which becomes a part of the ejaculated semen (which is also carried through the urethra). As men grow older, the tissue of the prostate often begins to enlarge, a condition called hyperplasia. As the bulk of the prostate enlarges, the gland begins to constrict the portion of the urethra passing through the prostate and thus prevent the normal flow of urine, a condition known as benign prostatic hypertrophy or hyperplasia (BPH). As BPH develops, one or more constricted or stenotic regions within the prostatic urethra can from time to time obstruct the flow of urine; so the signs of BPH are difficulty starting urination, dribbling following urination, reduced force of the stream of urine, a tendency to urinate frequently in small amounts as well as pain and discomfort. As a result an increase in urinary tract infections can occur. The symptoms are common; 75%-80% of men over the age of fifty are affected. See, for example, the Harvard Medical Health Letter: September 1988; Volume 13; Number 11; pages 114 4 and Castaneda, Flavio et al.; "Prostatic Urethra: Experimental Dilation in Dogs"; Radiology: June, 1987; pp. 645-648. In fact recent statistics apparently reveal that a 50 year old man has a 20-25% chance of undergoing treatment for this condition during his lifetime. See Castaneda et al., supra. It is currently estimated that about 500,000 prostatectomies (the most common method of treatment), are performed each year in the United States alone. See Castaneda, Flavio et al.; "Benign Prostatic Hypertrophy: Retrograde Transurethral Dilation of the Prostatic Urethra in Humans" Radiology; June, 1987, pp. 649-653.
When the obstructive symptoms of BPH become bothersome, the constricted portions of the urethra are usually reopened surgically. Current accepted treatment for BPH involves either open or transurethral surgery, which is costly and is associated with an acceptable but undesirable degree of mortality (estimated from 1.3% to 3.2%--see Castaneda, Flavio et al.; "Benign Prostatic Hypertrophy: Retrograde Transurethral Dilation of the Prostatic Urethra in Humans" Radiology; June, 1987, pp. 649-653) and With a significant degree of morbidity, especially in less fit patients.
The most common surgical procedure for BPH, as an alternative to open surgery, is a transurethral resection of the prostate, or TURP. The transurethral resection involves inserting a resectoscope through the urethra. A spring wire, adapted to carry an electric current, is inserted through the resectoscope for use in removing tissue. The wire carries one current for cutting away "chips" of tissue with the resectoscope and another current for cauterizing the remaining tissue to minimize bleeding. As much as two cubic inches of tissue are removed in this way.
The TURP surgical technique is not trivial nor inexpensive, though the actual procedure can ordinarily be done within one hour. The procedure carries similar risks as many of those associated with other general surgical procedures, including those associated with the use of general anesthesia. In addition, intraoperative irrigation fluids are required to flush blood from the prostatic urethra while tissue is being removed creating a danger that the flushing fluid will enter the blood circulatory system through iatrogenic openings into veins causing fluid overload and possible death, a result known as "post-TURP" syndrome. Other surgical hazards include stricture formation at the urethra or bladder neck, post-manipulation pain or bladder spasm, urinary tract infections, and reactive urethral swelling which can cause urinary obstruction and epididymitis. Other complications include retrograde ejaculation and delayed recurrent obstruction of the bladder neck area. Further, the post-operative care following a TURP procedure requires a prolonged hospital stay, creating substantial costs for medical care. The appropriate DRG (Diagnostically Related Group), currently designated by Medicare, for the TURP procedure presently entails an average length of hospital stay of 5.8 days. For a discussion of current pressures to reduce allowable Medicare fees for the TURP procedure and the impact of such reduced fees on urological patient care and the American urologist, see Holtgrewe, H. L. et al.; "Transurethral Prostatectomy: Practice Aspects of the Dominant Operation in American Urology"; The Journal of Urology: volume 141 (1989); pp. 248-253. In addition, some men have reported sexual dysfunction following the resection. Certain men have also become incontinent as a result of the surgery because of inadvertent damage done to the external sphincter muscles positioned at the apex of the prostate for controlling urine flow. The surgery usually results in moderate discomfort with some post-operative bleeding being usual.
As a result of the trauma that many men experience from TURP and the relatively long in-patient care required for post operative recovery, alternative techniques of treating BPH are being investigated. For example, using hormonal treatments to prevent or reverse prostate enlargement has long been considered in the treatment of prostate enlargement. Male hormones are known to promote growth of the gland. However, there have been some uncertainties about the role played by hormones in creating BPH. Other devices for treatment of the prostate utilize heat, as for example a device sold by Armonite, Inc. of New York. The latter device provides thermal therapy to the prostate transrectally by radiating the prostate with microwave heat which is claimed to result in the shrinkage of the affected prostate tissue. The long term results of such therapy are currently inconclusive.
Methods of injecting medications directly into the prostate through a catheter extending into the prostatic urethra have been attempted. However, these injections are frequently ineffective due both to the poor absorption of such medications by the prostate, as well as to the difficulty inherent in positioning and retaining the catheter with respect to the affected area, and generally result in reoccurring prostatic disorders. An example of a device for positioning such a catheter and injecting medications into the prostate is shown in U.S. Pat. No. 3,977,408 issued to MacKew.
Another approach to treating BPH is a technique known as transurethral balloon dilation of the prostate. In this approach a catheter having an inflatable balloon positioned on the distal end of the catheter is transurethrally inserted into the portion of the urethra extending through the prostate. The balloon is then inflated so that the expanding balloon dilates the urethra and is held in its inflated state for a limited period of time, e.g., between ten and sixty minutes. See, for example, Castaneda, et al.; "Prostatic Urethra: Experimental Dilation in Dogs"; Radiology; June, 1987, pp. 645-648; and Castaneda, et al.; "Benign Prostatic Hypertrophy: Retrograde Transurethral Dilation of the Prostatic Urethra in Humans" Radiology: June, 1987, pp. 649-653. See also U.S. Pat. No. 4,660,560 issued to Lester Klein. The balloon described in the last mentioned Castaneda et al. article is inflated at a pressure of between 3 and 6 atmospheres and held under pressure for about ten minutes. During the balloon dilation procedure the tissue of the urethra must be expanded beyond its normal elastic limit otherwise the urethra will not remain dilated for very long. Accordingly, the balloon is sized to expand, for example, to a 25 mm diameter so as to cause the tissue within the averaged sized urethra to stretch to the point of actually tearing or cracking so that when the tissue heals, permanent fissures will remain so that the urethra will remain dilated. But even expanding the tissue just beyond the elastic limits does not necessarily insure long term effects on relieving the stenosis and constriction of the urethral walls due to the nature of the resilient muscle tissues and large bulk of the hypertrophied prostate which has a tendency to rebound after temporary compression. See U.S. Pat. No. 4,762,128 issued to Rosenbluth. Accordingly, the latter patentee proposes to insert a stent in the prostatic urethra after being dilated by the balloon and removing the stent at a later time. The problem with inserted stents is that they are difficult to remove once they are inserted and there is a tendency for irritation and encrustation.
The use of laser radiation has been described for acutely (intraoperatively) removing tissue of the prostate gland by ablation (vaporization) so as to remove tumors or all or part of the gland as an alternative to the electrocautery resection technique described above. See U.S. Pat. No. 4,672,963 issued to Dr. Israel Barken and Smith, Jr., Joseph A. et al.; "Laser Photoradiation in Urologic Surgery"; The Journal of Urology: Vol. 31, April, 1984, pp. 631-635, cited therein. However, use of a laser to acutely remove tissue from the prostate by ablation would not necessarily reduce post-operative bleeding and trauma, impotence and incontinence. This problem of using laser energy to remove prostatic tissue relates to the manner in which laser energy is applied. Specifically, in order to remove tissue acutely the laser energy is applied through a fiber with the tip of the fiber positioned transurethrally essentially directly in contact with the prostate tissue. Direct contact with the tip of a fiber transmitting laser energy causes tissue to quickly reach 100.degree. C., wherein the tissue water vaporizes creating steam and an explosion, referred to as the "popcorn" effect. This method of tissue destruction is also poorly controlled and inefficient for removal of substantial amounts of tissue. For one, the tip of the laser fiber can become covered with charred tissue and require frequent cleaning. In addition, characteristics of the tissue itself, such as the amount of adenoma versus the amount of stroma, and the amount of blood within the tissue affect overall laser action. For example, blood at the tissue surface at the prostatic urethra highly absorbs Nd:YAG laser energy, causes superficial charring (carbonization), and, therefore, reduces tissue penetration by the laser, whereas blood flow beneath the tissue surface conducts heat away from the tissue and requires longer exposure time before the tissue will exceed 100.degree. C. and be ablated.
The device described in U.S. Pat. No. 4,672,963 uses a computer to continuously adjust the amount of laser radiation transmitted to the prostate during the procedure. Accordingly, the device includes an ultrasonic probe, inserted transrectally or positioned externally, for imaging the prostate in real time during the procedure so as to provide real time data regarding the destruction of the prostate tissue so as to enable the computer to adjust the laser radiation accordingly. Transrectal and external ultrasonic imaging of the prostate are well known as further suggested by Sanders, R. C. et al., "Update on Prostatic Ultrasound", Urologic Radiology 1987; Fleischer, Arthur C., "Prostatic Endosonography--A Potential Screening Test"; Diagnostic Imaging. April 1987, pp. 78-82; and Lee, Fred, "Prostatic Evaluation by Transrectal Sonography: Criteria for Diagnosis of Early Carcinoma", Radiology. Vol. 158, pp 91-95, January, 1986.
Other uses of a laser for removing constrictions of a stenotic region of upper air passageways by vaporizing tissue with a laser beam to form radial cuts in the stenotic region of the air passageways has been suggested--see Shapshay et al.; "Endoscopic Treatment of Subglottic and Tracheal Stenosis by Radial Laser Incision and Dilation"; Annals of Otology, Rhinology & Larvngology: Vol. 96, No. 6, November-December 1987, pp. 661-664.